MSU Extension Fruit & Nuts

Weather

Last week began hot and cooled off. Highs were in the 90s driven but hot humid air from the south. The weekend was cooler with highs in the 90s. No significant rain has fallen since June 27. Soils are beginning to dry out especially sandy soils. Late planted row crops are wilting in the mid-day heat. A few spots in southwest Michigan are still very wet from heavy June rains.

We have not had any significant rain in two weeks with hot, dry temperatures. The region has received about a third of an inch of rain, and the evaporation rate is very high at 0.2 to 0.24 inch per day for a total water demand of about 2.7 inches. Shallow-rooted berry crops need to be irrigated.

Hot weather will return this week with highs near 90. There is only a chance of thunderstorms this week so rain will be spotty. Our heat accumulation is about two weeks ahead of normal.

Tree fruit

San Jose scale crawlers from the first generation are beginning to settle and form scales. Japanese beetles are out. More will emerge after rain events. Ripe wild berries such as black raspberries, mulberry and bush honeysuckle provide a nursery for spotted wing Drosophila (SWD). SWD numbers are building. More traps are catching flies and traps near wild ripe fruit are catching a lot of flies. This hot weather is hotter than SWD likes, this will increase the time between generations. See the Spotted Wing Drosophila website for more information on SWD. Brown marmorated stink bug (BMSB) juveniles can be found. They will mature into flying adults in late July.

Apricot harvest is underway. Fruit are relatively free of bacterial spot symptoms.

Peach and nectarine hand thinning is winding up. Early peaches are starting to color. Estimated peach harvest dates are available on Enviroweather. Redhaven harvest is projected to begin about Aug. 1. Desiree peach in the Southwest Michigan Research and Extension Center (SWMREC) variety trial are crunchy ripe with Harrow Diamond starting to develop red coloration. Fungicide treatment for brown rot are needed as fruit background starts to lose its green color. Yellowing leaves due to bacterial spot is evident for susceptible varieties. The oriental fruit moth second generation flight is underway. Branch end flagging and fruit entries by first generation oriental fruit moth larvae are common at some sites. 

Sweet and tart cherry harvest continues. SWD numbers in the southwest region are increasing, especially near crops and wild plants with ripe fruit. Trap catches in cherry orchards are up. Maintain insecticide coverage for SWD until harvest is finished. See "Managing Spotted Wing Drosophila in Michigan Cherry'" from MSU for more information. Defoliation in the tree tops by cherry leaf spot is common. Cherry leaves are always susceptible to cherry leaf spot infection and need to be protected to preserve the leaves. Ripening cherries are very susceptible to brown rot.

Plum fruit should be protected against apple maggot. We are catching apple maggot. Codling moth and oriental fruit moth also attack plums. SWD can be a problem in plums as they ripened. Plums become susceptible when they soften to approximately 3 pounds firmness, measured without skin, using a fruit firmness gauge fitted with a pear tip. Brown rot is a threat as fruit ripens.

Apple fruit entries by oriental fruit moth and codling moth larvae appeared about two weeks ago. Codling moth trap catch numbers are low indicating the end of the first generation flights. The second flight of oriental fruit moth should begin soon. Obliquebanded leaf roller summer generation larvae have been actively feeding for two weeks. Apple maggot adults have been flying for three weeks. Apple maggot is a summer pest which emerges following rains. Sooty blotch and fly speck symptoms are expected in most of southwest Michigan, so fungicides effective should be included in cover sprays. Higher, exposed sites have fewer wetting hours and less risk due to these diseases so far.

Obliquebanded leafroller larvae are feeding in apples and many other fruits. Notice the green body, black head and shield behind the head. Photo by Bill Shane, MSU Extension. 

Pear fruit are growing rapidly. Pears become attractive to codling moth attack when they soften close to harvest. Pear psylla numbers are relatively low. Hand pulling of water sprouts will discourage psylla build up. Early season fungicide treatment for pear scab prevents initial infection by Fabraea. Once pear scab season passes, continue fungicide treatment for Fabraea leaf spot may be required in wet seasons if the disease is established on leaves.

Small fruit

Grapes are nearing berry touch. Black rot on the fruit and phomopsis on the stems are easy to find in ‘Concord.’ We are also seeing powdery mildew on the leaves. In ‘Niagara’ we can find downy mildew on the leaves. Old botrytis infections are fairly common in the berry clusters and growers should include fungicides with good action against botrytis in fungicide sprays before the berries touch and the cluster tightens. See "Controlling Botrytis bunch rot in grapes" for more information. Otherwise, wine grapes seem fairly clean.

Black rot has a distinctive pattern, where the rot starts at the initial infection and then spreads across the berry. Concord fruit will soon be resistant to infection by black rot. Photo by Keith Mason, MSU. 

The second flight of grape berry moth is underway, and there are eggs on the clusters. We are seeing fresh stings in berries. Scout vineyards for stings. Larvae in the berries are protected from sprays and will form the third generation. It may take a second spray to get through the second or third generations of grape berry moth. It’s too early to tell if we will have a fourth generation of berry moth this year, but if the hot weather continues that will become more likely. Japanese beetles, brown marmorated stink bug nymphs, grape leafhopper and potato leafhopper are scarce.

The tunneling by grape berry moth is seldom as visible as it is in the cluster of Vignoles. Photo by Keith Mason, MSU.

Blueberry harvest is underway. Early varieties such as Duke and Bluejay and others are being harvested. Bluecrop hand harvest has begun. The fruit is ripened quickly in the heat. Extremely hot conditions last week caused sunburn or sunscald in ripening fruit when the heat cooked exposed fruit. Some of this damage is easy to see but apparently good fruit will soften quickly after packing. We are seeing early ripening fruit on Jersey and other midseason varieties. This fruit is susceptible to SWD and should be protected or harvested. Many blueberry fields are becoming very dry and need to be irrigated. Growers are applying fungicides and insecticides to protect ripening fruit against rots and SWD.

Blueberry maggot are out. Sprays for SWD are effective against blueberry maggot. Blueberry stem galls are becoming easy to find. This is not a major pest in the southern growing region of Michigan. Blueberries have a shallow root system and under these hot conditions need an inch of water every three or four days. See "Irrigating Michigan blueberries" from MSU Extension for more information.

Strawberries have been renovated. Irrigate to promote new growth. As new leaves emerge, they should be protected from potato leafhopper, which stunts strawberry growth.

Brambles harvest is underway. Red and black raspberry are being picked. Blackberries are still green. Japanese beetles are out and more will emerge after any significant rains. Target Japanese beetle as soon as you see it to prevent this pest from aggregating in your fields. SWD traps should be out to monitor this pest. Raspberries and blackberries are a preferred host for SWD and the fruit needs to be protected.

Cranberry bloom continues.

Current berries are ripening and these berries need to be protected from SWD.

Upcoming meetings

The Michigan Grape Society is hosting a Grower Social at Fenn Valley Vineyards Wednesday, July 11, at 4 p.m. The cost is $20. RSVP to Carla at 269-561-2396 or nedbalek@fennvalley.com.

There is a free, two-day workshop on using drones in bush and tree fruit at the Southwest Michigan Research and Extension Center Aug. 9-10. Attendees will:

• Learn the essential elements required to safely conduct commercial flight and mapping operations in the National Airspace System including flight planning and preparation.
• Take part in hands-on drone flights both manual and autonomous.
• Develop an understanding of analysis techniques and applications in precision agriculture.
• Gain a brief overview of Remote Sensing and its management applications.
• Leave the course with a clear understanding of the Drone-to-GIS workflow, including planning and completing missions, processing data and analyzing said data in GIS.

If you are interested in attending, please register and answer the questions. Space is limited. Interested parties must sign up by July 25. We will confirm your spot by Aug. 1. Please contact Erin Bunting (ebunting@msu.edu) or Bruno Basso (basso@msu.edu) for more information

Related articles

• Michigan State University Spotted Wing Drosophila website
• Control of American brown rot
• Cherry leaf spot 101: Understanding Blumeriella jaapii biology and management
• Banning black rot and Phomopsis from young grape clusters
• Using the MSU Enviroweather grape berry moth model in 2018
• Irrigating Michigan blueberries
• Blueberry weed control: late spring and summer options
• SWD recommendations for raspberries and blackberries